Palladium(I) tri-tert-butylphosphine bromide dimer {[Pd (PtBu3) (μ-Br)]2} is an active catalyst for cross coupling reactions. Palladium(I) tri-tert-butylphosphine bromide dimer has been prepared by Mingos et al using either Pd2dba3.C6H6 or a combination of Pd2dba3.C6H6 and Pd(COD)Br2 (J. Chem. Soc. Dalton Trans. (1996) 4313 and J. Organomet. Chem. 600 (2000) 198). Pd2dba3.C6H6 itself is prepared by crystallising Pd(dba)2 in a large volume of C6H6. Pd2dba3.C6H6 is a highly air-sensitive catalyst which requires high vacuum and low temperature conditions for crystallisation.